Field of the Invention
The present invention relates to a liquid discharge head.
Description of the Related Art
Liquid discharge heads that discharge liquid, such as ink, are known. In a liquid discharge head, a print element substrate having discharge port rows is mounted on a support member, and a liquid chamber inside the support member and supply ports, which are provided in the print element substrate so as to correspond to the respective discharge port rows, are connected to each other, forming liquid flow paths that are continuous from the liquid chamber to discharge ports. In recent years, due to the demand for high-speed recording, the number of discharge ports arranged in the liquid discharge head has been increased, and a flow path design that enables liquid to be supplied at a high flow rate is required.
Because liquid discharge heads handle fluid, such as ink, vibration of liquid causes menisci to vibrate at the discharge ports, which may deteriorate the discharge accuracy. The meniscus vibration tends to occur in liquid discharge heads that have a large number of discharge ports arranged in a high density and that have high liquid flow rates per unit time.
For example, when liquid discharge from the plurality of discharge ports is stopped at once, the inertial force that causes the liquid to move forward of the discharge ports increases, pushing out the liquid in the discharge ports and extruding out the menisci inside the discharge ports. Meanwhile, a typical liquid tank, which supplies liquid, is configured to be maintained at a negative pressure to prevent dripping of liquid from the supply port. Hence, the liquid supplied from the liquid tank is subjected to a force that tends to pull the liquid back to the upstream side (liquid tank side). Therefore, the liquid with the menisci extruding out at the discharge ports, as described above, subsequently tends to retract in to the opposite side.
As has been described, when the discharge is stopped, so-called meniscus vibration, in which menisci extrude out and retract in at the discharge ports, is induced. This vibration becomes large as the liquid flow rate per unit time increases.
When the subsequent discharge is performed in a state in which the menisci extrude out, fine ink droplets are splashed, whereas, when the subsequent discharge is performed in a state in which the menisci retract in, the discharge speed and the amount of discharge decrease. In either case, defective discharge, such as discharge irregularity, occur.
Furthermore, in a state in which the discharge is stopped, when liquid discharge from the plurality of discharge ports is started at once, the liquid starts to move from the stationary state. Therefore, after the first discharge of liquid, the inertial force that causes the liquid to move forward of the discharge ports may not be increased to a magnitude sufficient to fully fill the discharge ports with the liquid. Thus, when the subsequent discharge is started in a state in which the menisci in the discharge ports retract in, defective discharge, such as discharge irregularity, occur.
Japanese Patent Laid-Open No. 2006-240150 discloses a liquid discharge head in which meniscus vibration at discharge ports can be reduced. The liquid discharge head disclosed in Japanese Patent Laid-Open No. 2006-240150 has, in a liquid chamber, a buffer chamber that stores gas (for example, bubble). By using the gas in the buffer chamber, the meniscus vibration at discharge ports is absorbed and attenuated.
In recent years, demands for high image quality and reliability are more and more increasing. Under the circumstances, if liquid has been discharged or has not been discharged for a long time, gas dissolved in liquid, gas taken in after passing through a housing of a liquid discharge head, or the like may be combined with the gas in the buffer chamber, increasing the volume of the gas in the buffer chamber. As a result, the gas in the buffer chamber may expand until it reaches the discharge ports and the vicinity thereof. In this state, the expanded gas blocks the liquid flow paths, preventing the liquid from being supplied to the discharge ports and causing defective discharge.
The present invention provides a liquid discharge head in which the meniscus vibration at discharge ports is suppressed and in which defective discharge can be reduced.